Pre-lamb Decision Guide

Given the complex nature of drench resistance which is becoming increasingly common throughout New Zealand, we encourage you to use this as a guide only and we strongly recommend that you consult with your animal health advisor on the best approach for your farm and flock. Be aware, blanket drenching of all ewes should be avoided.

Do you plan to drench your ewes pre-lambing?*

Yes

No

Blanket drenching of ewes is not recommended

If you have some of the risk factors identified below (in conjunction with other risk factors identified on the next page), selective drenching of part of your flock could/may be beneficial.

Your ewes have symptoms of worms*

i.e., high faecal egg count, ewes under stress, weight loss, diarrhoea, dag score less ≥ 3.

Yes

No

High larval challenge*

High pasture contamination with over-wintered larvae (eg lambs wintered on areas ewes will lamb onto), low pasture covers.

Yes

No

Low (<3) average BCS of the mob*

Ewes with lower body condition are more susceptible to worms.

Yes

No

Short pasture covers going into lambing*

Feed shortage due to low pasture growth rates, early set-stocking, intensive grazing or overstocking.

Yes

No

It’s likely that you do not need to drench your ewes prior to lambing! Continue to the vaccine guide.

Other factors to consider

Age of ewes?
Young ewes are more susceptible to worms.

Do you have existing drench resistance?
Based on your observations, 10-day drench checks or FECRT/drench test. This will alter product choice.

Pregnancy scanning results?
Ewes carrying multiples are more susceptible to worms.

Based on your answers to the previous questions you may need to drench a portion of your ewes. Seek advice from your Animal Health Advisor and continue to the vaccine guide.

Other tools to look into to help manage worms include:

• Improving ewe nutrition

• Refugia

• Cross-species grazing

• Genetics

Vaccine Guide

How long before lambing are you likely to pre-lamb vaccinate?*

>4 weeks

2-4 weeks

Don’t vaccinate pre-lamb

Do you use a pre-lamb drench containing levamisole?*

Yes

No

Do you scan and identify singles and multiples?*

Yes

No

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Term	Definition
Blanket drenching	The practice of drenching an entire flock.
Selective drenching	The practice of determining which members of a sheep flock require drenching and only drenching a portion of the total flock.
Body condition score (BCS)	A quick and easy, low-cost management tool assessing the amount of body fat or condition of a ewe by feeling the spine and short ribs along the loin area. Differential feeding of ewes based on body condition score can have a considerable impact on ewe flock performance.
Faecal egg count	Counts the numbers of worm eggs in faeces and is used to monitor worm burden in sheep.
Faecal egg count reduction test (FECRT)	A test to determine the effectiveness of drenches against worms on your farm at the time of testing. It does this by comparing the Faecal Egg Count (FEC) immediately before drenching, with the FEC 10 days after drenching. The result is reported as the percentage reduction in faecal egg count over this period.
Drench resistance	Occurs when there is a change in the genetic makeup of worms allowing them to survive exposure to a correctly applied dose of drench that would normally be lethal. The resistant worms carry on to breed passing their resistance genes to their offspring.
Refugia	The practice of making sure there are some susceptible worms able to reproduce, often by leaving a proportion of animals undrenched, so that the non-resistant (susceptible) worms continue to predominate.
Dag score	Dag scoring is an easy technique that assesses the ‘dagginess’ of a sheep and can be used as an indicator of likely worm burden and/or challenge.
Drench check	A faecal egg count of 10-20 animals within a mob 10-14 days after drenching to evaluate the effectiveness of the drenches that you have used. This is often done in-between, and in addition to, the more extensive and costly Faecal Egg Count Reduction Tests (FECRT) which should be done every 3-6 years.

Decision making guide for drenching and vaccinating ewes this pre-lamb

Blanket drenching of ewes is not recommended

Other factors to consider

Vaccine Guide

Glossary

Useful Links